Magnetism 2

xholonWorkbook.xml

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<Notes><![CDATA[
Khan Academy
------------
Title: Magnetism 2
Description: Magnetic fields and their effects on moving electrical charges
Url: http://www.khanacademy.org/video/magnetism-2
InternalName: magnetism-2
YoutubeId: NnlAI4ZiUrQ
Keywords: physics, magnetic, field, cross, product

My Notes
--------
Magnetic fields
visualization
  field lines
  bar magnet with N pole and S pole
  convention is to draw lines from the N pole to the S pole
    imagine a hypothetical monopole trying to escape from N to get to S
  another way to think about it 2:30
    a compass pointer would be tangent to the field lines
    N pole of compass pointer points to S pole of magnet

magnitude of a magnetic field at any point
  defined in terms of the effect it has on a moving charge
a magnetic field is an electromagnetic field moving at a high/relativistic speed

example  
  B (B⃗) is a vector that's a magntic field
  the force (F) on a moving charge (proton, electron, etc.)
    = the magnitude of charge
    * (the velocity of the charge CROSS the magnetic field)
  F = Q · (v × B) where F, v and B are vectors( F⃗ v⃗ B⃗ ) and Q is a scalar
  
the cross product is concerned with vectors that are perpendicular to each other
  if v is exactly perpendicular to B, then F has a value
  if they are parallel, then there is no impact
  F is perpendicular to both v and B

magnitude of the force F
  |F⃗| = Q * |v⃗| * |B⃗| * sin θ
    where θ is the angle between v and B

units of the magnetic field B
  sin θ has no units
  F is Newtons (N)
  Q is Coulombs (C)
N = C * m/s * (Bunits)
N*s/(C*m) = Bunits
  Newton seconds per Coulomb meter
  1 Bunit is 1 Tesla (T)

Stuff to do::
  write code to draw a bar magnet, with field lines between the poles
    SVG (use JavaScript, Raphael, etc.)
  write code to do the various calculations

]]></Notes>

<script implName="lang:python:inline:"><![CDATA[
print "height = 12.34 m"
]]></script>

<script implName="lang:javascript:inline:"><![CDATA[
print("height = 56.78 meters\n");
]]></script>

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  <Block/>
  
  <!-- quantities -->
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<PhysicalSystem>
  <Block>
    <Height>0.1 m</Height>
    <ElectricCharge>0.0 C</ElectricCharge>
    <MagneticFluxDensity>0.0 T</MagneticFluxDensity>
  </Block>
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<Blockbehavior implName="lang:python:inline:"><![CDATA[
# This works if pasted in as a last child of Block.
height.incVal(0.02)
print("Python wants something to do. Height:" + str(height))
]]></Blockbehavior>

<Blockbehavior implName="lang:javascript:inline:"><![CDATA[
// This works if pasted in as a last child of Block.
height.incVal(0.02);
print("JavaScript wants something to do. Height:" + height + "\n");
]]></Blockbehavior>

<Blockbehavior implName="lang:bsh:inline:"><![CDATA[
// This works if pasted in as a last child of Block.
height.incVal(0.02);
System.out.print("Java/Beanshell wants something to do. Height:" + height + "\n");
]]></Blockbehavior>

<Blockbehavior implName="lang:jruby:inline:"><![CDATA[
require 'java'
# This works if pasted in as a last child of Block.
$height.incVal(0.02)
puts "Ruby wants something to do. Height: #{$height}"
]]></Blockbehavior>

<Blockbehavior implName="lang:groovy:inline:"><![CDATA[
// This works if pasted in as a last child of Block.
height.incVal(0.02);
System.out.print("Groovy wants something to do. Height:" + height + "\n");
]]></Blockbehavior>

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<?xml version="1.0" standalone="yes"?>
<!--
"Bar Magnet with N and S" created using Google Docs; it doesn't know about SVG rect
https://docs.google.com/drawings/d/1PSWaxBhufGAjxSx9MSgV4XdcESBfUN6NOa-aEh66V3I/edit
-->
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